1. Field of the Invention
This invention generally relates to a chip packaging structure. More particularly, this invention relates to a chip packaging structure for coupling with an external circuit having a plurality of signal conducting legs.
2. Description of the Prior Art
The trend of development of electronic products is to make the product having characteristics such as smaller size, higher transfer speed, and higher pin count. The evolution of the packaging technique of a chip, including the driving chip of the liquid crystal display, basically follows this trend. Among the packaging techniques, a Chip On Film (COF) process is able to make the electronic product have the above characteristics and can be used on a flexible circuit board. Therefore, the COF process is a suitable packaging technique for the driving chip of the liquid crystal display.
In a flip chip packaging process, a chip is overturned and mounted face downward on a substrate via metal conductors. Since the chip is fixed on the film and merely electrically coupled with the flexible substrate via metal conductors, the flip chip process is called COF packaging process when it is applied to the flexible substrate. However, as the number of conducting points of the driving chip of the liquid crystal display increases, the distance between the conducting points becomes smaller, resulting in a narrower lead that is connected to the conducting point. Consequently, the leads in the stress area break more easily when the flexible substrate is bent under a force.
FIG. 1 is a schematic view of a conventional chip packaging structure. The chip packaging structure 80 includes a flexible plate 10, a chip 30, and a plurality of leads 50. The chip 30 includes a plurality of non-signal conducting points 31 and a plurality of signal conducting points 32. The plurality of leads 50 are disposed on the flexible plate 10 and include a plurality of non-signal leads 51 and a plurality of signal leads 52. The plurality of non-signal leads 51 respectively extend from the plurality of non-signal conducting points 31 and outwardly from the chip 30. The plurality of signal leads 52 respectively extend from the plurality of non-signal conducting points 31 and outwardly from the chip 30. The non-signal leads 51 are so called “Dummy Leads” since no signal is transmitted thereon. In other words, outside the chip 300, the non-signal leads 51 substantially “occupy” a certain space. The conventional chip packaging structure is still improvable.